Acceptability of COVID-19 self-testing among social and clinical vulnerable populations using a decentralized testing model in Abuja, Nigeria; A mixed methods analysis of an implementation study.

Diagnostic testing is critical during infectious disease outbreaks, enabling timely patient management and isolation to reduce transmission and mortality. During the COVID-19 outbreak in Nigeria, testing rates remained low due to limited access to centralized RT-PCR sites. To expand access, the National COVID-19 Testing Strategy (January 2021) introduced decentralized self-testing models targeting vulnerable populations. This study assessed the uptake of decentralized COVID-19 testing and the acceptability of self-testing among socially and clinically vulnerable populations in Abuja, Nigeria. A mixed-methods study was conducted across four primary health centres (PHC), four community pharmacies (CP), and four patent medicine stores (PMS) between October 2022 and May 2023. Symptomatic individuals received provider-delivered testing at PHC or provider-delivered/self-testing at CP and PMS using antigen rapid diagnostic tests (Ag-RDT). Social vulnerability was defined by low education, illiteracy, or low wealth; clinical vulnerability by age ≥ 50, unvaccinated status, or comorbidities. Testing uptake and acceptability were analyzed using logistic regression, while in-depth interviews (IDI) explored preferences for testing sites and methods. Of 1,586 individuals screened, 1,368 were eligible and 1,322 (96.6%) accepted testing. Most tests occurred at PHC (53.5%), followed by PMS (25.9%) and CP (20.7%). Social vulnerability was higher among PMS users than PHC users (OR = 1.37; 95% CI 1.05-1.77), while clinical vulnerability was lower at CP (OR = 0.24; 95% CI 0.16-0.35) and PMS (OR = 0.28; 95% CI 0.19-0.39) compared to PHC. Self-testing acceptability was high (93.4% at CP; 92.1% at PMS). Outcome of IDI highlighted trust in CP/PMS providers, proximity, convenience, and affordability as key drivers of testing uptake, with self-testing widely preferred across vulnerability groups. Decentralized testing through CP and PMS reached more socially vulnerable individuals and demonstrated high self-testing acceptability. Leveraging these outlets in outbreak responses could enhance equitable access to diagnostic testing in future pandemics.